1. Field of the Invention
This invention relates generally to hot-gas cleanup systems and more particularly to a filter assembly that includes an all metal fail-safe/regenerator device, a metal filter housing and either a metallic or ceramic type filter element that has an integral locking means, requires only a single primary external particulate barrier seal, and allows ease of attachment of the fail-safe/regenerator device to the filter housing. Ceramic type filter elements may also have one or more secondary gasket type seals.
2. Background Information
Modern industrial methods have resulted in a need for an apparatus that is capable of efficiently filtering high temperature combustion gases containing particulate material. In combustion turbine applications, for example, a combustion turbine uses energy generated from hot pressurized combustion gases produced by burning natural or propane gas, petroleum distillates or low ash fuel oil. When coal and other solid fuels are burned, particulates carried over from the combustion of such solid fuels can cause turbine blade erosion and fouling. An efficient system for filtering of such hot combustion gases would permit the use of such solid fuels. As another example, in conventional boiler operations, the boilers undergo routine shutdown for cleaning the fireside surfaces and for inspection. An efficient hot gas filtering system would greatly extend the life and operational time for a boiler to operate between inspections. Fouling of the fireside surface due to ash deposition and corrosion would be eliminated or minimized.
Also, as a key component in advanced coal-or biomass-based power applications, hot gas filtration systems protect the downstream heat exchanger and gas turbine components from particle fouling and erosion, cleaning the process gas to meet emission requirements. When installed in either pressurized fluidized-bed combustion plants, pressurized circulating fluidized-bed combustion plants, or integrated gasification combined cycle plants, lower downstream component costs are projected, in addition to improved energy efficiency, lower maintenance, and elimination of additional expensive fuel or flue gas treatment systems. As a critical component, long-term performance, durability, and life of the filter elements and associated high temperature gasket seals are essential to the successful operation of hot gas filtration systems in advanced combustion and gasification applications.
U.S. Pat. Nos. 5,185,019 and 5,433,771 (Haldipur et al. and Bachovchin et al., respectively) disclose a thick walled hot gas candle filter mounting assembly with no seal that is external to the side of the fail-safe/regenerator type device shown, and with separate locking means. However, Haldipur et al. teaches a side pin thread arrangement and Bachovchin utilizes a bottom-retaining ring 72. U.S. Pat. No. 5,474,586 (Eaton et al.) discloses a thin walled hot gas candle filter mounting assembly, and discusses gasket assemblies generally. It too has no external side seal between a fail-safe means and the filter housing, here 12, and also has a separate locking means, annular flange 74. U.S. Pat. No. 5,876,471 (Lippert et al.), provides a filtering apparatus that can filter aggressive, high temperature, high-pressure gases, having an improved, double gasket assembly that can be employed with a conventional ceramic candle filter or a thin walled ceramic composite filter. It has no side seal between a fail-safe means, here 68, and the filter housing. It also has a separate locking means 78. This system uses a complicated series of sleeving and gaskets.
Additionally, U.S. Ser. No. 09/263,436, filed on Mar. 4, 1999, now U.S. Pat. 6,123,746 provided an improved gasketing assembly, with an optional fail-safe/regenerator, and described possible use of metallic filter elements having the same connection and configuration as standard ceramic candle filters. There, no side seals between a fail-safe means 68 and the filter housing were shown, and a separate locking means 78 was used.
U.S. Ser. No. 09/393,561, filed on Sep. 10, 1999, now U.S. Pat. 6,273,925 describes an all-metal fail-safe/regenerator filter device which fits within a filter housing 62 and has two seals 70 and 73 external to the fail-safe/regenerator 67 and between the filter housing and the fail-safe/regenerator device, as well as a separate locking means 78 which comprises a two flat portions, one portion being of the filter housing 62 and the other being of the locking means, with a threaded hole perpendicular to the threaded surfaces, and with a bolt threadably engaging the threaded holes. This device also requires an outwardly extending radial flange 71. This flange is defined as being machined at right angles to the device wall 69 or square at the top and beveled at the bottom.
All of these various designs have a variety of advantages, but most require a large number of seals and locking means, adding to complexity, cost and difficulty of substitution.
As a result, there is a need to develop use of better and simpler connections within the filter assembly for advanced coal-fired and other higher temperature operation applications, that would be resistant to combinations of sulfur and steam contact at high temperatures, and which would be able to substitute easily into existing systems in the field with a minimum of part substitution. It would also be desirable to have a minimum number of seals reducing the number of degradable components and increasing reliability.
Therefore, it is a main object of this invention to provide an improved filter assembly and fail-safe/regenerator device having strengthened, simpler connections that are resistant to steam, sulfur, alkali, chlorides, and other contaminants found in steam laden coal gas.
It is a further object to provide a simplified design that can easily substitute into existing units.
These and other objects are accomplished by providing a filter assembly for holding a filter element within a hot gas cleanup system pressure vessel, said filter assembly comprising:
(a) a tubular filter housing, said filter housing having a parallel top inner wall and bottom inner wall, where the top wall has a smaller inner diameter and where a joint is formed where the walls join, where the bottom wall ends in an integral outward-extending flange with holes therethrough, said walls defining an interior chamber;
(b) a one piece, all metal, tubular fail-safe/regenerator device, having a parallel top wall and bottom outer wall, where the top wall has a smaller outer diameter and where a joint is formed where the walls join, said walls and joint mating with the inner walls and the joint of the filter housing, and where the bottom wall contains an integral outward-extending flange with holes therethrough which mate with the holes in the filter housing flange;
(c) one essential sealing means consisting of one compliant gasket separate and apart from the filter housing and fail-safe/regenerator device, said compliant gasket positioned between mating joints of the filter housing and fail-safe/regenerator device, said gasket effective to provide a seal between the filter housing and the fail-safe/regenerator device; and
(d) a porous filter element body attached at the bottom of the metal fail-safe/regenerator device. The fail-safe/regenerator device can have a long extension which can be welded to a filter element body, when the filter element is made of metal.
The invention also resides in a filter assembly for holding a filter element within a hot gas cleanup system pressure vessel, the filter element including a porous body having two opposing ends, one defining an attachable open end and the other defining a closed end; the filter element body having a uniform inside diameter, said filter assembly for holding a filter element comprising:
(a) a tubular filter housing, said filter housing having a top end, a bottom end, and a certain axial length and having peripheral inner sidewalls composed of a uniform inner diameter top surface and a larger uniform inner diameter bottom surface defining a first top portion and a second bottom portion, with an inner joint formed where the two portions converge, and where the bottom end has a flat surface perpendicular to the larger uniform inner diameter surface of the bottom portion, said bottom flat surface having at least one hole therethrough, perpendicular to said bottom flat surface, said sidewalls defining an interior chamber;
(b) a one piece, all metal, tubular fail-safe/regenerator device, having a top portion and a second bottom portion, disposed within the interior chamber of the filter housing, where the top portion has a parallel top outside wall and the bottom portion has a parallel bottom outside wall with an outside diameter larger than the top outside wall, where a joint is formed where the two portions converge, where the outside surfaces of the fail-safe/regenerator device mate with the inside surfaces of the filter housing, the outer surfaces of the fail-safe/regenerator device having a joint opposite the inner joint of the filter housing, and where the bottom end has a flat outside surface mating to the bottom end flat surface of the filter housing, said bottom flat outside surface having at least one hole therethrough opposite the at least one hole through the bottom flat surface of the filter housing, the device also having heat transfer media disposed between a screening means at the top of the device within the filter housing and a screening means at the bottom of the device for particle capture;
(c) one essential sealing means consisting of one compliant gasket separate and apart from the filter housing and fail-safe/regenerator device, said compliant gasket positioned between the joints of the filter housing and the fail-safe/regenerator device, said gasket effective to provide a complete seal between the filter housing and the fail-safe/regenerator device;
(d) a porous filter element body attached to the bottom of the metal fail-safe/regenerator device outside of the filter housing; and
(e) means to attach the filter housing and fail-safe/regenerator device through the opposing holes in each bottom flat surface.
The invention also resides in a metal fail-safe/regenerator device with a metallic-type filter element attached by welding. A modified bottom end of the fail-safe/regenerator device and a metal adapter ring may be used to mate and form an attachment between a porous ceramic filter element and the fail-safe/regenerator device.
Such a design utilizes a very strong essentially all metal type design which can be used with a metal type porous filter element made of a superalloy which is corrosion resistant in porous form in the presence of steam, alkalis, chlorides, or with standard, thick-walled ceramic type porous filter elements. This design allows quick and easy repairs in the field, being compatible with most prior art units.
The design disclosed herein also integrates the fail-safe/regenerator, holder mount, and porous metal, intermetallic or metallic/ceramic composite media into an integral, single unit. Said unit utilizes a single, compression fit, compliant gas seal when retrofitably installed into particulate filtration systems in advanced coal-based power systems and/or biomass and industrial applications. An integral fail-safe/regenerator-holder mount concept is similarly disclosed for use with ceramic monolithic, filament wound or composite filter elements, in conjunction with standard compliant gas sealing and mounting assemblies.